Field
The disclosed concept relates to electrical switching apparatus, such as, for example, circuit breakers. The disclosed concept also relates to movable arm assemblies and movable arms for electrical switching apparatus.
Background Information
Electrical switching apparatus include, for example, circuit switching devices; circuit interrupters, such as circuit breakers; network protectors; contactors; motor starters; motor controllers; and other load controllers. Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. Small power switches, which are commonly referred to as miniature circuit breakers, are used, for example, in residential and light commercial electrical distribution systems. Miniature circuit breakers typically include a set of separable electrical contacts. The separable electrical contacts are in physical and electrical contact with one another when it is desired that the circuit breaker energize a power circuit. When it is desired to interrupt the power circuit, the separable electrical contacts are separated. This is generally accomplished by way of a movable arm. More specifically, one of the separable contacts (e.g., a movable contact) is located at an end of the movable arm, and when the movable arm moves away from the other separable contact, the power circuit is interrupted. In many known miniature circuit breakers, the other end of the movable arm (e.g., the end opposite the movable contact) interfaces with an operating handle of the circuit breaker.
In order for the circuit breaker to be properly certified, such as, for example and without limitation, to be properly certified by Underwriters Laboratories Inc., headquartered in Northbrook, Ill., the circuit breaker must be able to interrupt predetermined currents without failing. Testing in connection with ensuring certification criteria are satisfied has shown that the interface between the movable arm and the operating handle becomes undesirably hot. As a result, the operating handle, which is commonly made of thermoset materials, will be exposed to performance degradation in the form of an inability to act as an effective insulator.
There is thus room for improvement in electrical switching apparatus, and in movable arm assemblies and movable arms therefor.